sprinkler touble

I am using plastic impact sprinklers. they refuse to return and get stuck. Have tried 5 different sprinklers but no luck. we run them off of a well. there is sufficient pressure since we can run 4 on a zone. the sprinklers i have trouble with are on a zone of 2 sprinklers. what am i doing wrong! surely all these i have tried aren't defective

We take many calls per week regarding this subject. I would say 90% of the time the problem is lack of pressure. Depending on the type of sprinkler you have (more information would be helpful on brand...) they might spray water just fine, but not have sufficient pressure to activate the return mechanism.
have you measured your pressure?
If the problem is low pressure I would suggest looking into a Sennenger Wabbler (http://www.sprinkler.com/buy/wobbler)which is perfect for low pressure applications-- it has an extremely even watering pattern as well. The only down side is that the ark can't be adjusted.
Hope this helps!